JP4521779B2 - Series winding motor and control method thereof - Google Patents

Description

  The present invention relates to a series motor having a contactless switching element for interrupting operation, which element is embodied in the form of an electronic switch.

  A machine tool is generally driven by an electric motor configured as a series-winding motor (a motor for both directions), and is controlled by a mechanical switch. Although electronic devices are becoming more and more common in machine tools, control of machine tools using only power semiconductors, which also serve to switch machine tools on and off, is considered unreliable. The reason is that the semiconductor can fail (internal short circuit), in which case it can no longer be controlled. In the case of a pure electronic switch with only a single switching path, what can happen is that a permanent connection occurs between the supply voltage and the motor, i.e. the motor can no longer be switched off or rotates immediately. Is to start doing.

  In order to achieve sufficiently reliable control of machine tools that use only electronic switches and no mechanical switches, the prior art allows a circuit breaker to be placed in parallel with the control switch that switches the motor on and off. Known, this circuit breaker trips the fuse if there is any failure in the control switch (see German Patent 3119794C2, German Patent 3432845A1, German Patent 40215559C1).

  However, this type of circuit works reliably only when irregular behavior is detected in the device and part of the electronic switching element, and the instrument can be put into a defined off state, and the instrument can be switched off in a defined off state. Any fault in the protection circuit can be detected to enter the state.

  In the prior art, only German Patent 3119794C2 addresses the problem of faults occurring in the protection circuit, but this invention requires the operator to test the protection circuit from time to time by pressing a push button. .

  Accordingly, an object of the present invention is a direct-winding motor and a method for controlling the direct-winding motor, and the motor can be reliably switched on and off using only an electronic switch while eliminating a mechanical switching element. Is to provide a method.

The purpose is an AC series winding motor, in particular an AC series winding motor for a machine tool, in which a first electronic switch (control switch) for switching the motor on and off and a control switch are connected in series. A second electronic switch (circuit breaker) connected to the control circuit, and a monitoring circuit for monitoring the function of the electronic switch and analyzing the potential at the connection point of the control switch and the circuit breaker, and further comprising an electronic controller, preferably a micro processor is coupled to the two electronic switches and monitoring circuits, and the monitoring circuit when the recorded failure of one of the electronic switches, is achieved in the block state of at least one of the electronic switch by forcing put straight winding motor.

  The technical problem of the present invention is thus completely solved.

BEST MODE FOR CARRYING OUT THE INVENTION

  According to the present invention, two electronic switches, ie one control switch and one circuit breaker, are connected in series, so that even if one of the two switches fails, the motor is reliably turned on and off. Can be switched. The monitoring circuit can reliably detect a failure of the control switch and / or circuit breaker, and can reliably force the motor into a safe off state. This means that manual monitoring of the system is no longer necessary. Instead, when the motor is switched on, a fault test is automatically performed and can be switched on only under the condition that no fault has been detected.

  In an advantageous development of the invention, means are provided for bridging the circuit breaker switching path with high impedance so that a functional test of the control switch can be carried out without having to start the motor.

  This prevents the motor from starting immediately when the circuit breaker is energized during the initial function test if the control switch is faulty. This high impedance bridge at both ends of the circuit breaker switching path allows the circuit breaker to be tested safely without the risk of starting the motor if the control switch fails.

  The means for the high-impedance bridge at both ends of the circuit breaker switching path can comprise, for example, an optocoupler, preferably comprising an opto-triac, connected in parallel to the main terminal of the circuit breaker via a resistor.

  Another way to prevent the motor from starting immediately if the control switch fails during a circuit breaker test is a means for monitoring the rotation of the motor, which means is coupled to the controller And providing a means by which at least one of the two switches can be forced into a blocking state if the motor starts when the circuit breaker is energized with the control switch not energized.

  This likewise avoids the danger of the motor starting immediately if the control switch fails during a circuit breaker test.

  The means for monitoring the rotation of the motor can be embodied in the form of a rotational speed sensor or can monitor the current of the motor. In the latter case, a shunt resistor is connected in series with the armature and the voltage drop across the resistor is monitored.

  There are various options for the configuration of the monitoring circuit for monitoring the potential across the control switch.

  A circuit with a transistor, a diode and two resistors is known from the prior art, for example US Pat. No. 6,236,177B1, but the present invention prefers a much simpler circuit.

  In a preferred development of the invention, the monitoring circuit comprises a voltage divider with two resistors connected in series, the first resistor being connected to the first pole of the auxiliary supply voltage, and the second resistor Is connected to one of the main terminals of the control switch and the second pole of the auxiliary voltage, and the connection point between the two resistors is connected to the other main terminal of the control switch via the third resistor, The output of the monitoring circuit is supplied to the input terminal of the controller.

  As a result, reliable monitoring can be achieved simply by using three resistors and in any case the supply voltage required for the electronic device.

According to an alternative embodiment of the invention, a series-winding motor, in particular for a machine tool , having a fuse, through which the armature is connected to the supply voltage via a first electronic switch (control switch) Thereby having a second electronic switch (circuit breaker) that can switch the motor on and off, connected in parallel to the armature and the control switch, and capable of removing the fuse in the event of a failure; A monitor having an electronic controller, preferably a microprocessor, coupled to the switch, having means for blocking the circuit breaker and testing the function of the circuit breaker in the blocked state, and analyzing the voltage drop at the control switch A circuit breaker, if its output signal is supplied to the electronic controller and the monitoring circuit records a failure of the control switch, That having a monitoring circuit that forces the tripping the Yuzu the object is achieved by direct winding motor.

  Even in this case, the technical problem of the present invention is completely solved.

  In the prior art, it was not possible to test the function of the circuit breaker in the event of a failure, but because the circuit breaker was placed in parallel to remove the fuse according to the present invention, the circuit breaker was blocked first and then In addition, it is possible to test safely without removing the fuse.

  For this purpose, in a preferred development of the invention, a transistor having an emitter and a collector, which can be conducted to test the circuit breaker by measuring its control current, comprises a control terminal and a main terminal of the circuit breaker. To prevent the fuse from being pulled out during circuit breaker testing.

  According to another advantageous embodiment of the invention, the electronic switch is embodied as a triac.

  Therefore, even in the case of alternating current, it is possible to switch a high load with almost no power loss, and at the same time, it is possible to use a control switch for adjusting power and controlling motor speed. There is this.

For the method, object of the present invention is further direct winding motor for AC, preferably a method of controlling a direct winding motor for AC for machine tools,
(A) connecting the motor to a supply voltage for alternating current in series with a second electronic switch (circuit breaker) via a first electronic switch (control switch) for switching the motor on and off;
(B) monitoring the potential across the control switch;
(C) when both of the switches are in an off state, if the potential across the control switch takes a value outside a predetermined threshold range, blocking the switch;
(D) when both switches are in the off state, if the potential across the control switch is within the threshold range, first turning on the circuit breaker;
(E) when the potential across the control switch takes a value outside the threshold range, turning the control switch on;
(F) blocking both switches if the potential across the control switch does not take a value outside the threshold range;
Achieved by a method comprising:

  According to the invention, a functional test is first performed before switching on the control switch to determine if the circuit breaker is working properly. If so, then the control switch is tested before it can be turned on to operate the motor.

  In this way, faults in the circuit breaker and / or control switch can be reliably detected. In such a case, disconnection of the circuit breaker or control switch is not dangerous because the motor cannot be started. During testing, any short circuit or disconnection of individual components of the monitoring circuit is required because a counter input signal is required at the input terminal of the electronic controller to determine whether the control switch and circuit breaker are working correctly. As a result, a safety off state is brought about. Driver circuit faults are also detected. This is because permanent excitation causes the same failure as a short circuit of the control switch or circuit breaker. In the absence of excitation, this results in the same behavior as when the control switch or circuit breaker is disconnected. In such a case, the motor cannot be started.

  In one advantageous development of the invention, if the potential does not increase when the circuit breaker is switched on with the control switch turned off, the circuit breaker is immediately switched off again.

  In this case, a fault exists in the control switch. By switching off the circuit breaker immediately, the motor is prevented from starting.

  For this purpose, according to a further development of the inventive method, the motor rotation is monitored and the motor rotation is recorded if the motor rotation is recorded when the circuit breaker is switched on with the control switch off. Immediately switch off again.

  In an alternative embodiment, to test the control switch, the circuit breaker is first bridged with high impedance and the test is performed to determine if the potential across the control switch increases to a predetermined threshold.

  Thus, even if there is a failure, it is possible to safely prevent the motor from starting during the test of the control switch.

Alternatively, an object of the present invention is a method for controlling a series motor, preferably a machine motor for a machine tool, comprising:
(A) The motor is connected to the supply voltage, the fuse and the first electronic switch (control switch) for switching the motor on and off, and the second electronic switch (circuit breaker) is connected to the supply voltage via the fuse. Connecting and
(B) testing whether the circuit breaker works by first blocking the circuit breaker and energizing the circuit breaker to test the control current before turning on the control switch;
(C) if it is found that the circuit breaker excitation is working properly, removing the circuit breaker block and turning on the control switch to turn on the motor;
(D) if a failure is detected during step (b), blocking the excitation of the control switch;
(E) monitoring the voltage drop at the control switch and triggering a circuit breaker to trip the fuse if the voltage drop when the control switch is switched off does not increase beyond a predetermined threshold;
Achieved by a method comprising:

  Thus, by connecting the circuit breakers in parallel, the circuit breaker driver circuit can be tested for failure before the control switch is turned on, and if the control switch fails, the operation can be stopped. .

  The features of the invention described above and described below may be applied not only in the combinations specified in each case, but also in other combinations or alone, without departing from the scope of the invention. It's obvious what you can do.

  Further advantages and features of the present invention are apparent from the following description of preferred embodiments with reference to the drawings.

  FIG. 1 shows an electric motor according to the invention in the form of a series-winding motor circuit, which is indicated in its entirety by the reference numeral 10.

  The motor 10 is supplied with 230 V from the two electrodes 24 and 26 of the AC voltage source. The motor 10 has an armature 12, and its field winding (not shown) is wound in series and connected to one electrode 24 of the supply voltage. The other electrode of the armature 12 is connected to the other electrode 26 of the supply voltage via two triacs in series, that is, the circuit breaker 16 and the control switch 14. The control switches 14 and control terminals 28 and 30 of the circuit breaker 16 are connected to terminals of an electronic controller 18 in the form of a microprocessor. The electronic controller 18 is likewise connected to the two electrodes 24 and 26 of the supply voltage source and is additionally supplied with a supply direct current (if this supply voltage is not yet integrated in the electronic controller 18). The monitoring circuit 20 is also connected on the one hand between the control switch 14 and the circuit breaker 16 and on the other hand to the second pole 26 of the supply voltage source, which on the one hand is connected to the control switch 14 and the circuit breaker. 16 monitors the potential between 16 and on the other hand the second pole 26 of the supply voltage source, the output of the monitoring circuit being coupled via line 32 to the input terminal 22 (pin 1) of the electronic controller 18. Yes.

  Due to the phase control of the control switch 14, the electronic controller 18 also performs a soft starter function when the motor is switched on and a speed and / or power control function during motor operation in a substantially known manner. .

  In order for the monitoring circuit 20 to confirm that both the control switch 14 and the circuit breaker 16 are working without problems, a functional test can now be carried out before switching on the electric motor 10.

FIG. 2 shows a preferred embodiment of the monitoring circuit 20. An auxiliary voltage, which may be the supply voltage _VCC for the electronic controller 18, is supplied to one main terminal of the control switch 14 via a voltage divider, and this main terminal is connected to the second electrode 26 of the AC power supply. The voltage divider consists of resistors _{R 1} and _{R 2.} The voltage divider tap is connected to the input terminal 22 (pin 1) of the controller 18. Tap of the voltage divider is also coupled to a connection point between the third resistor controlled via the R ₃ switch 14 and circuit breaker 16.

  Such a monitoring circuit provides a very simple way to monitor the potential across control switch 14 using only three components.

  In alternative embodiments of the invention, other monitoring circuits such as those known from US Pat. No. 6,236,177 B1 may be used. Such a circuit is shown in FIG. 3 and is here designated by reference numeral 20 '. However, a monitoring circuit as shown in FIG. 2 is preferred because of its simpler structure.

  A modified embodiment of the electric motor according to the present invention is shown in FIG. 4, which is here designated in its entirety by the number 10a. In this and further modifications described below, corresponding reference numbers are used for corresponding parts.

The only difference between the electric motor 10a and the embodiment of the electric motor 10 of FIG. 1 is that an additional means 36 for the high impedance bridge of the circuit breaker 16 is provided. The means 36 for the high impedance bridge circuit breaker 16 is composed of a resistor opto-triac 38 that is connected in parallel to the main terminals of the circuit breaker 16 through R _4. The opt triac 38 is excited by the LED 40.

  FIG. 4 also shows one of the two field windings, designated by reference numeral 13, in series with the armature 12.

  Here, how the direct winding motor 10 or 10a operates will be described.

In the circuit shown in FIGS. 1 and 2, an initial test is first performed before the electric motor 10 is first switched on, thereby causing the input terminal 22 (pin 1) of the microprocessor 18 via line 32. It is determined whether the output voltage of the monitoring circuit 20 sent to is within a predetermined threshold range. This can be seen in more detail in FIG. While the supply voltage _VCC is applied across R ₁ and the potential across R ₂ is zero, an AC voltage at the connection between the control switch 14 and circuit breaker 16 is applied to pin 1 via R _3. Supplied. When the control switch 14 and the circuit breaker 16 is in the off state, the AC voltage across R ₃ not is added at all, as a result, the voltage of pin 1 is determined by the exclusively divider R ₁ and R ₂ and V _CC . For example, if V _CC = 5V and R1 = R2, and the control switch 14 and circuit breaker 16 are not working, the threshold range where the voltage at pin 1 should be is 2.5V ± 0.5V.

  If so, the first test has been passed. This test confirms that the blocking effect has been tested for both positive and negative half waves.

  If not, there is a fault in the circuit. Either the circuit breaker 16 is faulty, i.e., shorted, the driver circuit for the circuit breaker 16 is faulty, or the monitoring circuit 20 is faulty. In this case, the control switch 14 is not energized and the microprocessor 18 switches to a safe fault state (off state).

  If the first test is passed, then the circuit breaker 16 is excited via line 30 when switched on, as shown in FIG. In this case, the circuit is functioning properly if the voltage at pin 1 fluctuates periodically, thereby exceeding the threshold shown in FIG. 2a. Otherwise it is out of order. Either the control switch 14 is faulty (short-circuited), the driver circuit for the control switch 14 is faulty, or the monitoring circuit 20 is faulty.

  If a fault exists, the circuit breaker 16 is switched off again as soon as possible, and the microprocessor 18 switches to a safe fault state (off state).

  If a failure (short circuit) of either the control switch 14 or the circuit breaker 16 is detected, the motor cannot be turned on. If the control switch 14 or the circuit breaker 16 is disconnected, the motor cannot again start, so this is not dangerous. With the circuit for the motor 10 as described above, the failure of the driver circuit can be detected together with the failure of the monitoring circuit. During testing, the “pass” function requires a counter input signal at the input terminal 22 (pin 1) of the microprocessor 18 so that any short circuit or disconnection of individual components of the monitoring circuit is consequently safe. Brings off state. Permanent excitation of either control switch 14 or circuit breaker 16 results in the same failure as a short circuit of the control switch or circuit breaker. If the microprocessor 18 is unable to output a control signal on line 28 and line 30 to excite the control switch 14 and circuit breaker 16, this produces the same result as disconnecting the control switch 14 or circuit breaker 16. In this case also, the motor cannot be started.

  In the circuit according to FIG. 1, if a fault is detected during the second test when the circuit breaker 16 is energized with the control switch 14 not energized, the circuit breaker 16 is immediately switched off again. This is very important. A delay in switching off the circuit breaker 16 upon detection of a failure during the second test will eventually start the motor, which may be inconvenient in certain circumstances.

  In order to eliminate this possibility, the motor 10a of FIG. 4 also comprises means 36 for the high impedance bridge of the circuit breaker 16.

  When test 1 is complete (the voltage at pin 1 is within the threshold range when the circuit breaker and monitoring circuit are not energized), the circuit breaker 16 is not energized, but is assisted by circuit 36 to It is only bridged by impedance. Thus, when the control switch 16 is short-circuited, it is possible to carry out a function test of the control switch 16 without causing the danger that the motor will start immediately.

  As an alternative to the circuit 36 for the high impedance bridge of the control switch 16, means for monitoring the rotational speed of the motor is shown as a further modification in FIG.

For this purpose, a shunt resistor R ₅ can be provided in series with the field winding 13. During the second test, that is, when switching on the circuit breaker 16 in order to test the control switch 14, the pressure drop across the shunt resistor R ₅ between the electrode 26 and the line 52 of the AC voltage is recorded Then, the excitation of the circuit breaker 16 is immediately interrupted, thereby preventing the motor from starting.

  Alternatively (or additionally), a rotational speed sensor 54 that monitors the rotor speed of the motor could be provided as shown in dashed lines in FIG. During the second test, i.e. when the circuit breaker 16 is energized to test the control switch 14, when the rotational speed sensor 54 receives a signal, the excitation of the circuit breaker 16 is immediately interrupted, thereby The rotation is stopped. Otherwise, the circuit of the motor 10b is the same as the circuit of the motor 10a.

  Another embodiment of an electric motor according to the present invention is shown in FIG. 6 and is generally designated by the number 10c.

  In this case, a meltable safety device 56 is provided that can be removed by the circuit breaker 16 in the event of a failure of the control switch 14. For this purpose, the circuit breaker 16 is connected in parallel to the two electrodes 24 and 26 of the supply voltage source immediately after the fuse 56. In this case, the potential drop across the control switch 14 is monitored by the protection circuit 20 as described above. The output from the monitoring circuit 20 is supplied to pin 1 of the microprocessor 18. A complete functional test is not possible with the circuit of FIG. 6 because the fuse 56 will respond immediately, but the driver circuit for the circuit breaker 16 is still tested by preventing triggering of the circuit breaker or triac 16. can do.

For this purpose, the gate 28 of the triac 16 is connected to the output terminal of the microprocessor 18 (pin 3) via two series resistors R ₆ and R _7. The connection point between the two resistors R ₆ and R ₇ is connected to the measurement input (pin 4) of the microprocessor 18 via a line 62. A transistor 60, whose base can be driven via the output terminal (pin 2) of the microprocessor 18, is arranged between the gate 28 of the circuit breaker 16 and the supply voltage electrode 26.

  For testing purposes, the monitoring circuit 20 is first evaluated. The test is performed as described in connection with FIGS. 2 and 2a. If a failure is detected during this test, the circuit breaker 16 is triggered to trip the fuse 56.

  If no failure is detected in the previous test, then the driver circuit for circuit breaker 16 is tested as follows.

In the first step, power is supplied to the base 64 of the transistor 60 via pin 2 of the microprocessor 18. This prevents the triac 16 from triggering. Here, a gate pulse is output via pin 3, whereby transistor 60 prevents triggering. Here, the voltage across resistors R ₆ and R ₇ can be detected at pin 4 of microprocessor 18. The output voltage at pin 3 corresponds approximately to the supply voltage _VCC . At this time, if no voltage is applied to the pin 4, either one of the resistors R ₆ and R ₇ is disconnected or the gate pulse is not output, which means that a fault exists. Assuming resistors R ₆ and R ₇ are identical, 1/2 V _CC, which is approximately half the supply voltage, must be applied to pin 4 while the gate trigger current is flowing. In this case, the driver circuit for the triac 16 is operating properly. If all the supply voltage V _CC is applied to the pin 4 when the gate pulse is output at pin 3, the resistor R ₆ are disconnected, this also means that the fault is present.

  If a fault is not detected, the power supply of transistor 60 via pin 2 is discontinued, thereby enabling the circuit breaker or triac 16 to operate during operation and the control switch 14 to trip the fuse 56 in the event of a fault. . The control switch 14 can then be switched on to switch the motor on. If the control switch 14 is no longer excited, i.e., no gate pulse is being output via line 30, the voltage drop across the control switch 14 must be above a predetermined threshold. Otherwise, the control switch 14 has failed. If the fault is detected when switching the control switch 14 off, the circuit breaker 16 triggers via pin 3 of the control circuit 18, thereby tripping the fuse 56.

1 shows a simplified circuit diagram of a first embodiment of a series winding motor according to the present invention; 1 shows a preferred embodiment of a monitoring circuit suitable for the motor of FIG. Across the input voltage of the resistor R ₃ of the monitoring circuit of Figure 2, and shows a graph of relation of the output voltage of pin 1, 2 shows an alternative embodiment of the monitoring circuit for the motor of FIG. An example of modification of the circuit of FIG. 1 shows a further modification of the circuit of FIG. Fig. 4 shows another embodiment of the present invention having a parallel circuit breaker for tripping a fuse.

Claims (4)

  A direct-winding motor, particularly a direct-winding motor for a machine tool, having a fuse (56), through which an armature (12) is supplied via a first electronic switch (control switch) (14) Connected to the voltage, thereby enabling the motor (10c) to be switched on and off, connected in parallel to the armature (12) and the control switch (14) and tripping the fuse (56) in case of failure A second electronic switch (circuit breaker) (16) capable of, and having an electronic controller (18), preferably a microprocessor, coupled to the switches (14, 16) and blocking the circuit breaker (16). And means (16) for testing the function of the circuit breaker (16) in the block state and a monitoring circuit (20) for analyzing the voltage drop at the control switch (14) Thus, if the output signal is supplied to the electronic controller (18) and the monitoring circuit (16) records a failure of the control switch (14), the circuit breaker (16) forces the fuse (56) to be tripped. A direct-winding motor having a monitoring circuit (20). A transistor (60) that can be turned on to test the circuit breaker (16) by measuring its control current comprises at its emitter and collector a control terminal (28) and a main terminal (44) of the circuit breaker (16). The series-winding motor according to claim 1 , wherein the series-winding motor is connected to prevent the fuse (56) from being removed during the test of the circuit breaker (16). The direct winding motor according to claim 1 or 2 , wherein the switch (14, 16) is embodied as a triac. A method for controlling a series-winding motor, preferably a series-winding motor for a machine tool,
(A) The armature (12) is connected to the supply voltage via the fuse (56) and the first electronic switch (control switch) (14) for switching the motor on and off, and the second electronic switch ( Connecting a circuit breaker) (16) to a supply voltage via a fuse (56);
(B) Before switching on the control switch (14), the circuit breaker (16) is first blocked, and the circuit breaker (16) is energized to test the control current by exciting the circuit breaker (16). Testing to work,
(C) if the circuit breaker (16) is found to be working properly, removing the block of the circuit breaker (16) and turning on the control switch (14) to turn on the motor; ,
(D) if a failure is detected during step (b), forcibly turning the switches (14, 16) to the OFF state;
(E) To monitor the voltage drop at the control switch (14) and to trip the fuse (56) if the voltage drop when the control switch (14) is switched off does not increase beyond a predetermined threshold Triggering a circuit breaker (16);
Including methods.

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